Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$231.41	10.823%	$256.4555	$256.46	$256.45	$256.50
Purchase #2	$175.40	3.546%	$181.6197	$181.62	$181.60	$181.60
Purchase #3	$30.35	7.605%	$32.6581	$32.66	$32.65	$32.70
Purchase #4	$48.52	12.356%	$54.5151	$54.52	$54.50	$54.50
Purchase #5	$37.30	3.773%	$38.7073	$38.71	$38.70	$38.70
Purchase #6	$105.83	5.871%	$112.0433	$112.04	$112.05	$112.00
Purchase #7	$43.39	5.460%	$45.7591	$45.76	$45.75	$45.80
7 purchase totals =	$672.20		$721.7581	$721.77	$721.70	$721.80